With the evolution in the information industry, a technology performing high speed transmission of diverse types of high capacity data is being required. In order to do so, by providing multiple distributed antennas within the conventional (or already-existing) cell, a Distributed Antenna System (DAS) method for resolving shadow areas and expanding coverage ranges is currently being developed.
The DAS corresponds to a system using multiple distributed antennas being connected to a single base station via wired connection or a through a dedicated line. Herein, the single base station manages multiple antennas being located in a cell, which is serviced by the base station, wherein each antenna is spaced apart from one another at a pre-determined distance. The DAS is differentiated from a centralized antenna system (CAS) in that multiple antennas are distributed at predetermined intervals within a single cell. Additionally, the DAS is differentiated from a Femto cell in that a central base station of the cell (or a base station located at the center of the cell) controls all of the distributed antenna areas within the cell, instead of having each of the distributed antenna unit autonomously control each area of the corresponding antenna. Moreover, the DAS is differentiated from a multiple hop relay system or ad-hoc network, wherein the base station is connected to a Remote Station (RS) via wireless connection, in that the distributed antenna units are connected to one another via wired connection or through a dedicated line. Furthermore, the DAS is also differentiated from a repeater structure, which simply amplifies a signal and transmits the amplified signal, in that each of the distributed antennas transmits a different signal to each of the neighboring user equipments based upon the command of the base station.
The above-described DAS may be considered as a type of multiple input multiple output (MIMO) system in that the DAS may support a single mobile station or multiple mobile stations by having each of the distributed antennas simultaneously transmit and receive different data streams. In light of the MIMO system, being configured of antennas distributed to diverse locations within the corresponding cell, the transmission area for each antenna is reduced, as compared to the CAS. Thus, the DAS may reduce transmission power. Additionally, by reducing the transmission distance between the antenna and the user equipment, path loss may be reduced, thereby enabling high speed data transmission to be performed. Accordingly, the transmission capacity and power efficiency of a cellular system may be enhanced, and communication performance of a quality that is relatively consistent as compared to the CAS may be yielded. Furthermore, by having the base station connected to each of the multiple distributed antennas via wired connection or through a dedicated line, signal loss may be reduced, and a level of correlation and interference between each of the antennas may also be reduced, thereby providing a high signal to interference plus noise ratio (SINR).
As described above, in order to reduce the cost for installing additional base stations and to reduce the cost for maintaining a Backhaul network, and in order to expand service coverage and to enhance channel capacity and SINR, the next generation mobile communication system may be alternately configured of the conventional CAS and the DAS, or the DAS may replace the conventional CAS so as to become a new basis of cellular communication.
Accordingly, in the related art mobile communication system, a CAS-based communication standard is required to support the CAS as well as the DAS.